Futurefic (a portmanteau of "future fiction") is a type of fan fiction that is set in the future relative to canon.
In terms of Forever Knight, any story whose temporal setting is after 17 May 1996 (when "Last Knight" aired) can be considered to be futurefic. This means that a story set in the late 1990s—at a time that is in our past—is nevertheless futurefic.
Equally, of course, stories set decades ahead (say, when the human characters from the series are in old age) are futurefic. However, although technically the term could also include stories set centuries from now, these are more likely to be referred to as science fiction.